Eco-evolutionary responses of soil microbes to drought stress

土壤微生物对维持陆地生态系统的碳平衡至关重要。微生物分解和稳定有机物的这种平衡会在环境条件改变的情况下发生变化。特别是干旱，降低了微生物的活动，影响了土壤的碳循环，并且由于气候变化正变得更加严重和频繁。微生物活性的降低可能是由于细胞水分胁迫和资源扩散和运输减少造成的限制的组合。干旱可以改变微生物的过程，因为耐胁迫微生物的选择是因为它们的竞争优势，或者因为耐胁迫能力是通过进化获得的。然而，这些生态和进化压力如何影响整个群落生理以应对干旱胁迫还没有被很好地理解。这给理解和预测干旱对微生物过程的影响和土壤碳循环的后果带来了不确定性。本博士项目旨在揭示微生物种群对干旱胁迫的响应机制，以及对整个群落特征和土壤碳循环过程的影响。其目的是研究在长期干旱下塑造社区的生态(选择性)和进化(适应性)过程。我们将使用基于特征的方法来探索人群水平上压力耐受和增长之间的权衡。将结合基于微生物培养、隔离和非培养的基于分子的种群基因组学来研究耐旱微生物。还将进行有针对性的实验室中观实验，以了解耐旱和对干旱敏感的种群对水分胁迫的反应及其对健康的影响。这种对种群水平的了解将用于评估应对干旱的群落变化，并预测有机物质分解和储存等生态系统功能。我们寻找一名对组学技术感兴趣的具有微生物学、生态学或土壤科学背景的博士生。我们将可以进入多个长期干旱处理的地点。将提供分子工具、生物信息学和生态统计学方面的研究培训。阿伯丁大学的基因组生物和医学中心拥有DNA测序平台，这些平台将用于该项目，包括培训。单个种群的基因组将通过培养分离株的基因组测序和从鸟枪式元基因组数据中重新组装个体基因组来获得。学生将获得气体和化合物特有的13C同位素分析的分析设施，以使用稳定的同位素示踪剂量化个别菌株的生长速度和生长产量等特征。学生将接受使用和应用这些尖端工具的培训，并将微生物组数据与生态系统措施相结合。微生物培养、种群基因组学和稳定同位素示踪方法的这种结合将使学生能够获得跨学科的独特技术技能，并将这些技能应用于应对与气候变化有关的关键挑战。

Soil microbes are critical in maintaining the carbon balance in terrestrial ecosystems. This balance of microbial decomposition and stabilisation of organic matter can shift under altered environmental conditions. Droughts, in particular, reduce microbial activity and affect soil carbon cycling, and are becoming more severe and frequent due to climate change. The reduction in microbial activity may occur due to a combination of cellular water stress and constraints imposed by decreased resource diffusion and transport.Droughts can alter microbial processes as stress tolerant microbes are selected due to their competitive advantage or as stress tolerance is acquired through evolution. However, how these ecological and evolutionary pressures impact overall community physiology in response to drought stress is not well understood. This brings uncertainty in understanding and predicting drought impact on microbial processes and consequences for soil carbon cycling.This PhD project aims to reveal the mechanisms of drought stress response in microbial populations and impacts on overall community traits and soil carbon cycling processes. The aim is to study the ecological (selective) and evolutionary (adaptative) processes that shape communities under long-term drought. We will use a trait-based approach to explore population-level trade-offs between stress tolerance and growth. A combination of microbial culture isolation-based and non-cultivation molecular-based population genomics will be used to study drought-tolerant microbes. Targeted lab mesocosm experiments will also be conducted to understand the response of drought-tolerant and drought-sensitive populations to water stress and the consequences on their fitness. This population-level understanding will be used to assess community shifts in response to drought and predict ecosystem functions such as organic matter decomposition and storage. We seek an enthusiastic PhD student with microbiology, ecology or soil science background with interest in omics technologies. We will have access to multiple sites with long-term drought treatment. Research training will be available in molecular tools, bioinformatics and ecological statistics. The Centre for Genome Enabled Biology and Medicine at University of Aberdeen houses DNA sequencing platforms which will be available to the project including training. The genomes of individual populations will be obtained through genomic sequencing of culture isolates and de novo assembly of individual genomes from shotgun metagenomics data. Analytical facilities for gas and compound-specific 13C isotope analysis will be available to the student to quantify traits like growth rate and growth yield for individual isolates using stable isotope tracers. Student will be trained in using and applying these cutting-edge tools and to integrate the microbiome data with ecosystem measures. Such a combination of microbial culturing, population genomics and stable isotope tracing approaches will allow the student to gain unique technical skills across disciplines and apply them to address key challenges linked to climate change.